Ever tried using an iPhone or Android phone to navigate with GPS through crowded streets? It’s pretty difficult, even for a veteran cyclist like me, to split my focus between the road and tiny symbols on the phone’s tiny screen.

Plugging in to a headset to hear turn-by-turn directions sometimes works, but cycling with headphones can also be a pain (not to mention illegal in places under certain conditions).

The answer, of course, is a heads-up display like Google Glass; but until it’s ready, there’s the Hammerhead, a light-powered navigation aid with some other cool tricks up its sleeve.